The length operator is denoted by the unary operator `#`

.
The length of a string is its number of bytes
(that is, the usual meaning of string length when each
character is one byte).

The length of a table `t`

is defined to be any
integer index `n`

such that `t[n]`

is not **nil** and `t[n+1]`

is **nil**;
moreover, if `t[1]`

is **nil**, `n`

can be zero.
For a regular array, with non-nil values from 1 to a given `n`

,
its length is exactly that `n`

,
the index of its last value.
If the array has "holes"
(that is, **nil** values between other non-nil values),
then `#t`

can be any of the indices that
directly precedes a **nil** value
(that is, it may consider any such **nil** value as the end of
the array).

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